Well, I wouldn't place much effort in defending myself against the leftards hysteria. It's a diversionary tactic. I would maintain a focus on the incoming masses and implement a deterrent.

If it were me (and it isn't, I know) I would send small boats out to intercept the ships carrying those 20,000 immigrants. The boats would float long lengths of steel cables on small buoys placed along the length of the cables in front of the incoming vessels, entangling the props and immobilizing the ship. After that, well......